The cell motility modulator Slit2 is a potent inhibitor of platelet function.

Vascular injury and atherothrombosis involve vessel infiltration by inflammatory leukocytes, migration of medial vascular smooth muscle cells to the intimal layer, and ultimately acute thrombosis. A strategy to simultaneously target these pathological processes has yet to be identified. The secreted protein, Slit2, and its transmembrane receptor, Robo-1, repel neuronal migration in the developing central nervous system. More recently, it has been appreciated that Slit2 impairs chemotaxis of leukocytes and vascular smooth muscle cells toward diverse inflammatory attractants. The effects of Slit2 on platelet function and thrombus formation have never been explored. We detected Robo-1 expression in human and murine platelets and megakaryocytes and confirmed its presence via immunofluorescence microscopy and flow cytometry. In both static and shear microfluidic assays, Slit2 impaired platelet adhesion and spreading on diverse extracellular matrix substrates by suppressing activation of Akt. Slit2 also prevented platelet activation on exposure to ADP. In in vivo studies, Slit2 prolonged bleeding times in murine tail bleeding assays. Using intravital microscopy, we found that after mesenteric arteriolar and carotid artery injury, Slit2 delayed vessel occlusion time and prevented the stable formation of occlusive arteriolar thrombi. These data demonstrate that Slit2 is a powerful negative regulator of platelet function and thrombus formation. The ability to simultaneously block multiple events in vascular injury may allow Slit2 to effectively prevent and treat thrombotic disorders such as myocardial infarction and stroke

SLIT2/ROBO-1: Novel Modulators of Vascular Injury

In atherosclerosis, infiltrating leukocytes and vascular smooth muscle cells (VSMCs) cause progressive vascular narrowing. Platelet-mediated thrombosis ultimately causes complete vessel occlusion, resulting in heart attack or stroke. In animal models and human patients, individually blocking these events is only partially effective. Another therapeutic strategy would be to globally target these multiple cell types. Slit proteins act as developmental neuronal repellents, and Slit2 via interaction with its receptor, Robo-1, impairs inflammatory recruitment of leukocytes and VSMCs. We detected Robo-1 expression in human and murine platelets. Using static and shear assays, we demonstrate that Slit2 impaired platelet adhesion and spreading on fibrinogen, fibronectin and collagen. Slit2 mediated these effects, in part, by suppressing activation of Akt but not Rac1, Cdc42, Erk or p38 MAPK. Slit2 also prevented ADP-mediated granular secretion. In mouse tail-bleeding experiments, Slit2 dose-dependently prolonged bleeding times in vivo. These data suggest a therapeutic role of Slit2 in atherothrombosis.MAS

SLIT2/ROBO1-signaling inhibits macropinocytosis by opposing cortical cytoskeletal remodeling

Macrophages survey their surroundings using macropinocytosis, but its regulation is unclear. Here, the authors report that SLIT2, a known inhibitor of Rac GTPases, is an endogenous inhibitor of macropinocytosis, and that SLIT2 limits the uptake of NOD2 ligands into immune cells and subsequent release of the inflammatory chemokine, CXCL1, in vivo

The cell motility modulator Slit2 is a potent inhibitor of platelet function

Background\u2014Vascular injury and atherothrombosis involve vessel infiltration by inflammatory leukocytes, migration of medial vascular smooth muscle cells to the intimal layer, and ultimately acute thrombosis. A strategy to simultaneously target these pathological processes has yet to be identified. The secreted protein, Slit2, and its transmembrane receptor, Robo-1, repel neuronal migration in the developing central nervous system. More recently, it has been appreciated that Slit2 impairs chemotaxis of leukocytes and vascular smooth muscle cells toward diverse inflammatory attractants. The effects of Slit2 on platelet function and thrombus formation have never been explored.Peer reviewed: YesNRC publication: Ye

The CXCR4/CXCR7/SDF-1 pathway contributes to the pathogenesis of Shiga toxin–associated hemolytic uremic syndrome in humans and mice

Hemolytic uremic syndrome (HUS) is a potentially life-threatening condition. It often occurs after gastrointestinal infection with E. coli O157:H7, which produces Shiga toxins (Stx) that cause hemolytic anemia, thrombocytopenia, and renal injury. Stx-mediated changes in endothelial phenotype have been linked to the pathogenesis of HUS. Here we report our studies investigating Stx-induced changes in gene expression and their contribution to the pathogenesis of HUS. Stx function by inactivating host ribosomes but can also alter gene expression at concentrations that minimally affect global protein synthesis. Gene expression profiling of human microvascular endothelium treated with Stx implicated a role for activation of CXCR4 and CXCR7 by their shared cognate chemokine ligand (stromal cell–derived factor-1 [SDF-1]) in Stx-mediated pathophysiology. The changes in gene expression required a catalytically active Stx A subunit and were mediated by enhanced transcription and mRNA stability. Stx also enhanced the association of CXCR4, CXCR7, and SDF1 mRNAs with ribosomes. In a mouse model of Stx-mediated pathology, we noted changes in plasma and tissue content of CXCR4, CXCR7, and SDF-1 after Stx exposure. Furthermore, inhibition of the CXCR4/SDF-1 interaction decreased endothelial activation and organ injury and improved animal survival. Finally, in children infected with E. coli O157:H7, plasma SDF-1 levels were elevated in individuals who progressed to HUS. Collectively, these data implicate the CXCR4/CXCR7/SDF-1 pathway in Stx-mediated pathogenesis and suggest novel therapeutic strategies for prevention and/or treatment of complications associated with E. coli O157:H7 infection